Installation manual

3
installation. Direct fired heaters are designed to
operate in a fresh flowing air stream. If the airflow
stops or is different from the factory settings, the
unit will shut down or perform below its design
capability. It is important to follow the installation
and start-up procedures to maximize the heater’s
performance. The manufacturer has designed a
unit that is easy to install, start up and service. If
you have any questions, call the Service
Department at 1-800-334-9256.
II. INTRODUCTION AND OVERVIEW
There are many types of heaters available for
commercial use. We will concern ourselves with
100% fresh air (make up air) Direct Fired Gas units
for commercial kitchen and industrial use. The
advantages of direct fired gas heaters include:
• Low cost per BTU of heating
• Readily available
• Most efficient heat transfer
There are two general types of gas-fired heaters,
direct and indirect. Indirect fired heaters, like a
residential furnace, burn gas inside a metal tube
called a heat exchanger. The air that is used to
heat the application is heated indirectly when it is
passed around the tubes. This air never comes in
contact with the flame. The combustion products
from the flame inside the tubes are exhausted
through a flue pipe to the atmosphere. A direct
fired heater burns the gas directly in the air stream.
The products of combustion are included in the air
that is used to heat the application.
III. APPLICATIONS
These direct fired heaters are well suited for a
wide range of uses in the commercial and
industrial field. For kitchen ventilation, where
heated make up air is needed in large volume in
cool climates, the direct fired unit is a prime choice.
It is able to handle large volumes of air with
substantial temperature rise at minimal expense.
The units are reliable, and most replacement parts
are readily available in the field.
Industrial plants and processes where there is a
large amount of air being exhausted are excellent
candidates for direct fired units. Where welding
hoods and plasma tables are used, the direct fired
unit can provide fresh outside air at a comfortable
temperature for occupants. Today the trend is
toward less user interaction with the heater units.
Most customers prefer the unit to sit on the roof, turn
on, and run by itself with no user interaction
(temperature selection, summer-winter selection,
etc.). This means that the field installation has to be
done properly; no user interaction can cover up
installation problems. Now, more than ever,
installation and start up is critical to customer
satisfaction and product operation.
IV. THEORY
Energy (heat) must be added to a specific volume of
air in order to change its temperature. Direct fired gas
heaters create heat by burning gas. Heat is measured
in BTU’s (British Thermal Units), which is a measure
of heat, not temperature.
Temperature vs. Heat
The temperature changes when the energy of a
specific volume of air increases or decreases. Energy
(in the form of heat) is added to a volume of air and
changes the temperature. When this energy is added
to different volumes of air, different temperatures are
achieved. To further illustrate this point, let’s look at
how to calculate temperature rise, i.e., the difference
between the air temperature after it is heated and
before it is heated.
BTU’s
∆T = --------------
CFM X 1.08
This equation shows that if the CFM’s increase and
the BTU’s remain constant, the temperature rise will
decrease. Conversely, if the CFM’s decrease and
the BTU’s remain constant, the temperature rise will
increase. (See following examples).